Question

is why did I do this is correct or why did I did this

Answer 1

Answer:

So the correct question will be, “Why did you do it?” 'Did' is a helping verb which tells us about past tense. According to grammar rule of tenses, we use first form of the verb with 'did' helping verb. So, “Why did you do it” ? is correct.

Answer 2

Answer:

"Why did I did this?" is correct answer

hope it help you,,MARK BRAINLIST